#include<stdio.h>

int main()
{
    int choice = 0;
    printf("please your choice:");
    scanf("%d",&choice);

    /*条件编译*/

    if (choice == 1)
    {
        printf("注册功能\n");
    }
    else if(choice == 2)
    {
        printf("登录功能\n");
    }
    else if(choice == 3)
    {
        printf("找回密码\n");
    }
    else
    {
        printf("error\n");
    }

     /*如果当前语句没有break,那就顺序执行。*/
     switch (choice)
     {
    case 1:
        printf("注册功能\n");
        break;
    case 2:
        printf("登录功能\n");
        break;
    case 3:
          printf("找回密码\n");
          break;
    default:
          /*都不满足的情况*/
          printf("input error\n");
          break;
     }
      return 0;
}